IIRC we need to display a major need for such a closing path. Currently, we don't even have enough active close voters, so mods have to intervene in migrations anyway. Also, we get ~one migration every day on average. That's not much. I don't think that's enough to convince SE to give us the migration paths.
However, if we were to get migration paths, I'd suggest Math, SciComp, EE, and Academia. Maybe not Academia. Nobody on Physics has managed to decipher their FAQ, so it's better to leave it out of the fray.
Here's a snapshot of the migration stats (link for 10k users):
